Thread draw-off nozzles for open-end spinning devices have become known in the prior art in many different designs. The thread draw-off nozzles have the task of deflecting the spun yarn upon its drawing off from the spinning device, and of imparting a false twist to the drawn yarn. As a result, spinning stability can be substantially increased and a uniform yarn can be produced. When drawn off based on the rotation of the spinning rotor, the yarn circulates in the manner of a crank on the yarn deflecting surface of the thread draw-off nozzle, such that a relatively high temperature stress along with wear occurs at the thread draw-off nozzles, which can adversely affect the spinning process.
Therefore, in the prior art, common draw-off nozzles are designed in two parts and consist of a nozzle insert that contains the yarn-deflecting surface and is usually made of a ceramic material, along with a nozzle frame that carries the nozzle insert and serves to attach the thread draw-off nozzle in the open-end spinning device. In order to fix the thread draw-off nozzle in the open-end spinning device in an interchangeable manner, and thereby, upon a change of the material to be spun, undertake an adjustment of the draw-off nozzle, the shank of the draw-off nozzle or the nozzle frame is provided with a thread, such that the thread draw-off nozzle can be screwed into the open-end spinning device. Such a thread draw-off nozzle is shown, for example, in DE 103 30 767 A1. In principle, thread draw-off nozzles of this type have proven themselves, but have a comparatively large space requirement. However, with today's requirements for ever-increasing productivity, which are associated with ever higher rotor speeds of 160,000 rpm and higher and ever smaller rotor diameters, problems with accommodating thread draw-off nozzles in the open-end spinning device are increasingly arising. Thus, in addition to the draw-off nozzle, the fiber feed channel must also be accommodated in the part of the open-end spinning device carrying the thread draw-off nozzle, which can also be designed in the form of a channel plate adapter, whereas both must be accommodated in an extension within the opening of the spinning rotor.
Therefore, thread draw-off nozzles that get by without a nozzle frame have already been proposed. For example, EP 1 367 154 B2 shows a thread draw-off nozzle, which consists of ceramic and is directly pressed into a corresponding receiving bore of a channel plate adapter. Given the absence of a nozzle frame, the space requirement of the draw-off nozzle can be reduced, but, upon the replacement of the draw-off nozzle, it is necessary to replace the entire channel plate adapter.
EP 1 445 359 B1 also shows a draw-off nozzle that can get by without a nozzle frame. Herein, the channel plate adapter, which accommodates the nozzle, is at least partially made of a plastic material and features a clip closure and centering members for receiving the thread draw-off nozzle. The thread draw-off nozzle, which consists only of a nozzle insert, can be clipped into the channel plate adapter made of a plastic material. The replacement of the draw-off nozzle is easily possible; however, damage to the clip device can occur.
With the two thread draw-off nozzles last mentioned above, it is disadvantageous that separate molds are required for manufacturing the ceramic thread draw-off nozzles, in order to attach the extensions or the like for pressing or clipping into the open-end spinning device However, this is profitable only with very large unit numbers.